The present invention relates to a mechanism for feeding an optical pickup carriage of a recording medium reproducing device, and more particularly to a feeding screw mechanism for feeding an optical pickup carriage along guide shafts of a device for reproducing a recording medium such as a CD (compact disc).
In general, the reproducing device for reproducing a recording medium such as the CD is provided with a feeding screw mechanism for feeding the optical pickup carriage mounting the optical pickup for reproducing a recording medium along the guide shafts.
FIG. 4 is a plan view of a chassis 1 of a conventional reproducing device in which a disc clamp mechanism is omitted.
As shown in FIG. 4, a chassis 1 has a turntable 2 for centering and loading a recording medium, a feeding screw 4 rotated by a motor 3, and an optical pickup carriage 5 slidably mounted on a pair of guide shafts 6 extending in the radial direction of the recording medium loaded on the turntable 2, and having a full nut 5A engaged with the screw 4. An objective 7 is also mounted on the optical pickup carriage 5.
An end of the feeding screw 4 which is located on an outer periphery end of the loaded recording medium is engaged with an outer holder 8A securely mounted on the chassis 1.
Also, another end of the feeding screw 4 which is located on an inner periphery end of the loaded recording medium is engaged with an inner holder 8B which is slidably mounted on the chassis 1 in a direction of a shaft center of the feeding screw 4, and urged to the outer holder 8A by a torsion spring 9.
The motor 3 rotates the feeding screw 4 so that the nut 5A engaged with the screw 4 is moved on the feeding screw 4, thereby feeding the optical pickup carriage 5 along the guide shafts 6.
In the optical pickup carriage 5 employing the full nut 5A shown in FIG. 5a, the full nut 5A does not remove even if the reproducing device receives external shock. However, there may occur that the full nut 5A overruns either of ends of the feeding screw 4 and sticks in a non-threaded portion because of the inertia, so that the optical pickup carriage can not be moved.
In addition, since the engaging area between the full nut 5A and the feeding screw 4 is large, the accuracy of parts must be held above a predetermined level, which causes the manufacturing cost of the optical pickup carriage to increase.
In order to resolve such a problem, a half nut 5B shown in FIG. 5b has been proposed so as to prevent the nut from sticking in the non-threaded portion of the screw 4. The half nut SB is made of plastic for reducing the manufacturing cost and pivotally mounted on the optical pickup carriage 5, and further urged to the screw 4 by a coil spring 10. Thus, the half nut 5B is deflected from the non-threaded portion by compressing the coil spring so that the half nut does not stick in the portion, even if the half nut 5B is pushed out to either end of the feeding screw 4.
However, since the feeding screw 4 is urged by the torsion spring 9 to the outer holder 8A, it may occur that the feeding screw 4 and the optical pickup carriage 5 are moved to the inner holder 8B for an instant due to the external shock. In particular, since during the transportation of the reproducing device or the waiting state for the reproduction, the optical pickup carriage is positioned at an innermost position, the optical pickup carriage 5 severely bumps the inner holder 8B, causing the objective 7 to incline.
An object of the present invention is to provide a reliable and optimum mechanism for feeding an optical pickup carriage of a reproducing device.
According to the present invention, there is provided a mechanism for feeding an optical pickup carriage of a recording medium reproducing device having a chassis comprising, a feeding screw rotatably mounted on the chassis by holders provided at both ends of the feeding screw, the feeding screw being disposed in a radial direction of the recording medium loaded on the reproducing device, a half nut having a semicircular sectional shape, and mounted on the optical pickup carriage, the half nut having at least one thread which comprises a thick central portion engaged with the feeding screw and thin both side portions.
The holder provided at an outer end of the feeding screw is slidably provided on the chassis so as to be moved in the axial direction of the feeding screw, and urged by a spring to the feeding screw.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.